There are various standard interfaces for the transmission of data in digital form that must ensure that communications between the different parts that constitute a system occur in a reliable manner thanks to the correct interpretation of the data contained in these interfaces. Below, in the description, different standard interfaces are explained for 2 Mb/s and 512 kb/s.
There are also a great variety of internal interfaces that are normally employed by companies engaged in the design of communications equipments in order to make best use of the features available within a closed communications equipment or system, based, fundamentally, on criteria such as signals employed, signal availability, error protection, etc. In this respect, Alcatel has specified internal interfaces termed SBI*I1 and SBI*I2 for 4 Mb/s, the net information rate of which corresponds to that of the aforementioned standard interfaces of one 2 Mb/s channel and eight standard 512 kb/s interfaces, respectively. See, e.g., U.S. Pat. No. 5,060,229 to Tyrrell et al for background information concerning an internal interface of the "SBI" type.